1. Field of the Invention
This invention relates to oxy-fuel torches which are used for cutting ferrous metals. These cutting torches operate with a fuel gas and oxygen. Acetylene is a commonly used fuel gas; however, other types of fuel gas are also used, including, for example, natural gas, propane, hydrogen and MAPP gas. This invention also relates to oxy-fuel torches which can be removably connected to various attachments for welding, cutting, brazing or heating. These multi-purpose oxy-fuel torches also operate with a fuel gas and oxygen as previously described.
2. Description of Prior Art
Flashback is a potentially dangerous situation which can occur in oxy-fuel cutting torches and multi-purpose torches such as those described above. When a flashback occurs, it may cause damage to the equipment. In some instances, personal injury also results to the operator and/or those in proximity to the equipment. The present invention does not eliminate the occurrence of flashbacks. The purpose of the present invention is to reduce the possibility that a flashback will migrate from the torch upstream to other components in a typical oxy-fuel cutting system.
Those skilled in this art are familiar with the components in a typical oxy-fuel cutting system. The torch is releasably connected to an oxygen hose and a fuel gas hose. It is common in the industry for the oxygen hose to be colored green and the fuel gas hose to be colored red. These two hoses are typically assembled together to form a unitized hose bundle which is more convenient for the operator to manipulate in the work place.
The oxygen hose connects to a gas regulator which is in fluid communication with a cylinder shutoff valve mounted on the oxygen cylinder. Oxygen cylinders are also typically colored green. Industrial oxygen cylinders are typically rated for pressures of up to 3,000 pounds per square inch ("PSI"). The regulator is used to reduce the outlet pressure, going from the cylinder and into the oxygen hose which varies, depending on the size of the cutting tip. Generally speaking, the oxygen pressure at the outlet of the regulator may range between 20 and 65 pounds per square inch gauge ("PSIG"). Higher outlet pressures are used with larger sized cutting tips. Lower outlet pressures are used with lower sized cutting tips. The appropriate outlet pressure is best determined by reference to a tip chart which lists optimum pressures and flow rates for each different size tip. The oxygen connectors on the hose and regulator are a special size thread which is specified by the Compressed Gas Association ("CGA").
The fuel gas hose connects to a regulator which is in fluid communication with the cylinder shutoff valve on the fuel gas cylinder. Acetylene is a commonly used fuel gas for cutting torches, as described above. A typical acetylene cylinder is formed with an interior porous mass which is saturated with liquid acetone. Acetylene gas is absorbed by the liquid acetone to facilitate safe storage. When the cylinder shutoff valve is opened, the acetylene gas vaporizes and migrates to the top of the acetylene cylinder where it passes through the cylinder shut-off valve and the regulator into the fuel gas hose which feeds the torch. Industrial acetylene cylinders are typically rated for pressures of 400 PSIG at 105.degree. F. Outlet pressures of acetylene at the regulator vary, depending on the size of cutting tip in use and typically range between 1 and 15 PSIG. Larger cutting tips require higher pressures and smaller cutting tips require lower pressures. Again, the operator should make reference to a tip chart to determine optimal outlet pressures and flow rates. The fuel gas connectors on the hose and regulator are special size left-hand threads which are specified by the CGA to avoid confusion.
Flashback occurs when the flamefront migrates from outside the tip to the inside of the torch, which causes the torch to become very hot and, if allowed to burn, may even cause it to melt. The flamefront can also migrate upstream back into one or both hoses, causing them to burn or rupture. In some extreme situations, the flamefront may migrate further upstream into a regulator and/or a gas cylinder causing them to explode.
Various types of safety devices have been developed for use in typical oxy-fuel cutting systems. For example, U.S. Pat. No. 4,286,620 assigned to Victor Equipment Company, the assignee of the present invention, discloses a combination torch and check valve assembly, which is incorporated herein by reference. In this patent, which issued on Sep. 1, 1981, the check valves are internal to the torch and are designed to reduce the possibility of reverse flow of gases from the torch into the hose.
U.S. Pat. No. 4,409,002 discloses a utility torch having a head mixer, which patent is incorporated herein by reference. This patent is also assigned to Victor Equipment Company. The integral head mixer disclosed in this patent, which issued on Oct. 1, 1983, is also designed to reduce the possibility of a flashback migrating from the torch upstream to other components in a typical oxy-fuel cutting system.
Other devices known generally in the trade as "flashback arrestors" have been developed to reduce the possibility of migration of a flashback from the torch. A variety of these devices are disclosed by advertising brochures attached to the Information Disclosure Statement filed concurrently herewith. These flashback arrestors are sold in pairs as after-market accessories. Victor Equipment Company also sells, as an accessory item, a pair of flashback arrestors which can be connected between the torch and the hose in the oxygen flow path and the fuel gas flow path. Alternatively, the flashback arrestors can be connected between the hose and the regulator.
The flashback arrestor manufactured by Victor Equipment is marketed under the tradename FLAMEBUSTER. It includes a porous, powdered metal sintered arrestor and check valve which is designed to reduce the possibility of a flashback from migrating upstream of the sintered component. The porous flashback arrestor has numerous tortuous pathways through which a flamefront must pass in order to migrate further upstream into other components in an oxy-fuel cutting system. In most circumstances, a flamefront will be quenched as it attempts to move through the tortuous pathways in the porous metal flashback arrestor.
Victor Equipment also manufactures another accessory item which is marketed under the trademark FLAMEBUSTER PLUS. This accessory item includes a pair of flashback arrestors and check valves with quick hose connectors manufactured in a cartridge-like format. One cartridge is for oxygen and the other cartridge is for fuel gas. Numerous other competitors manufacture accessory units which include a flashback arrestor and check valves as described in the Information Disclosure Statement. These accessory items can be readily purchased at welding supply stores across the nation.
Porous metal flashback arrestors, including the present invention, are not foolproof devices and do not guarantee that the flamefront will be quenched in all circumstances. For example, if the porous metal flashback arrestor is overheated, it may not quench the flamefront. If the flashback arrestor has been exposed to numerous prior flashbacks, the tortuous pathways may be eroded, thereby reducing the quenching capability.
The after-market flashback arrestors sold by Victor Equipment and others are not universally used in the trade. A pair of after-market flashback arrestors typically costs $40 to $60 (1992 dollars). The additional cost deters some individuals from buying these after-market flashback arrestors and adding them to their oxy-fuel cutting systems. Some individuals are simply not safety conscious and do not see a need for these accessory items. If a pair of flashback arrestors have been installed on the job, they may sometimes be clogged with debris and be taken out of the system by the operator. Existing flashback arrestors sold as after-market items do not use the parts-in-place principle, nor can they be repaired. If they are clogged or otherwise malfunction, they must be replaced.
Some of these after-market accessory items are rather heavy and cumbersome and, if attached to the torch, may adversely affect the balance thereof which is irritating to the operator. Because these after-market accessories are readily removable, the operator may take them off of the torch and install them between the hose and the regulators. Although this affords protection to the regulator and cylinders, it leaves the hose vulnerable to flashback.
Those skilled in the art will recognize that cutting torches are reconditioned on an "as needed" basis. In a typical fabrication plant, an operator will go to a tool crib and be issued a torch for a specific project. At the conclusion of that project, the torch will be returned to the tool crib. This sort of heavy industrial use eventually renders the torch unsuitable for further cutting. The tip may be clogged or other malfunctions may occur such as damage to various components of the torch.
The tool crib foreman will have a large number of cutting torches in supply, depending on the size of the plant. When a torch ceases to function properly, it will be set aside until a suitable quantity of malfunctioning torches have been accumulated. These malfunctioning torches will then be sent to a welding supply shop or to a reconditioning shop which will recondition the torches and bring them back to operational specifications. Torches manufactured by Victor Equipment Company are reconditioned many times during their useful life span, which may be as long as ten or twenty years. It may be necessary during the useful life of these torches to replace the flashback arrestor, if any, on one or more occasions, depending on the nature of use to which the torch is exposed. Existing flashback arrestors are not subject to repair. If they are to be replaced, a new pair must be purchased. This added expense deters replacement of flashback arrestors in existing systems during reconditioning.
The present invention includes a torch which has a pair of replaceable flashback assemblies which are formed as an integral part of the torch handle. These flashback assemblies are easy to replace and cost less than a pair of after-market flashback arrestors. This invention uses the parts-in-place principle (PIP) as an additional safety feature. If a flashback assembly is removed, the torch handle can no longer be connected to the hose. Removal of one or both of the flashback assemblies therefore renders the torch inoperative.
The present invention does not prevent the occurrence of a flashback. Rather, the invention is designed to reduce the possibility that a flashback will migrate upstream from the torch handle into the hose, regulators or gas cylinders. The invention is intended to provide an added measure of safety. The invention is not foolproof and, under certain circumstance, it will not prevent migration of a flashback upstream from the torch handle into the hose or elsewhere.